An electric machine, e.g., an electric machine for driving a hybrid vehicle or electric vehicle, generally has a rotor which during the operation of the electric machine can frequently be accelerated above a rotational speed of 15,000 rpm (revolutions per minute).
If a rotor which is rotating at such a speed has an unbalance, specifically if the mass of the rotor has an asymmetry about the rotational axis of the rotor, this can lead to undesired vibrations and increased wear on the electric machine.
In such an electric machine it is therefore absolutely necessary to perform balancing of the rotor in order to reduce or avoid vibrations or wear on the electric machine.
It would be conceivable to balance the rotor by selectively removing or adding weight material from or to the rotor, in a similar way to how balancing of a car tire is carried out by adding the balancing weights to the rim.
Alternatively, selective removal of weight material from the rotor can be carried out by selective milling or drilling. It proves disadvantageous with such a solution for balancing the rotor that the rotor has to be provided in advance with the additional weight material for later selective removal, which gives rise overall to a relatively heavy weight of the rotor and therefore also to relatively high moments of inertia on the electric machine.
An alternative conceivable solution for balancing the rotor by selectively adding weight material, such as for example by applying balancing pastes to the rotor, is very difficult to implement and also costly with a standard or automated fabrication process.